A personal computer generally comprises a PC board, a power supply unit, a cooling fan, a floppy diskdrive, a hard diskdrive, a speaker, and a plurality of card guides. For supporting these parts inside the personal computer, a metal frame is commonly used and then covered with a cover shell. This metal frame has holes and lugs for mounting. The housing of the personal computer is generally comprised of a substantially U-shaped cover shell covered on the metal frame, and a front panel secured to the cover shell. This U-shaped cover shell can be injection-molded from plastics or made from metal by stamping, however it cannot be used for both the horizontal computer and the vertical computer. Therefore, different cover shells shall be used for different types of computers. If the cover shell of a personal computer is injection-molded from plastics, the molding cost is expensive. If the cover shell of a personal computer is made from metal by stamping, it can only have a paint-coated smooth outer surface, which does not attract consumers. Furthermore, if a metal cover shell is used, many screws shall be used to fix it to the metal frame. This complicated installation procedure greatly consumes much labor. Nowadays, plastic housings are commonly used for personal computers. These plastic housings are commonly comprised of a plurality of panels assembled together. However, because these panels are fastened together by screws, the assembly process still consumes much labor.